1. Field of the Invention
The present invention is directed to a method and a device for separating undesired and desired signals and for dissipating the undesired signals and in particular to a method and a device having Off-line and In-line signal interference reduction device (SIRD) in communication systems, such as RF, IF, data, and voice communication systems, where undesired signals degrade the performance.
2. Description of Related Art
In communication systems, filters have been used to eliminate undesired signals such as interferences from the communication system. In every case, the related art sends both the desired and undesired signals through a filtering system to eliminate the undesired signals. Since the desired signals are sent through the filtering system, insertion losses due to the switches and the resistive, capacitive, and inductive loads of the filtering system weaken the desired signals.
Japanese Kokai 58-201423 to Haruyama discloses a comb-line filtering system to eliminate white noise and impulse noise in a sound signal system. The comb-line filtering system consists of a splitter, switches and resistors. In Haruyama's communication system, both the undesired and desired signals pass through the filtering system. The filtering system eliminates the undesired signals. The desired signal is summed up by the amplifier. Because the desired and undesired signals need to go through the filtering system, the desired signal is effected by insertion losses.
U.S. Patent No. 4,963,945 to Cooper et al disclose a band rejection filtering arrangement using bandpass filters, each terminated by a matched load. A quadrature hybrid circuit device divides the input signals and applies them to the bandpass filters. Signals within the rejection band are dissipated by the filters and matched loads, whereas desired signals are reflected. The reflected signals are then combined by the quadrature hybrid circuit to provide the band rejected output. This arrangement is made switchable between an all pass mode and the band rejection mode by providing PIN diodes between the quadrature hybrid circuit and the bandpass filters.
U.S. Pat. No. 3,788,674 discloses a filtering system for attenuating narrow band interference. The systems comprises: a broadband power splitter; a plurality of narrowband filters; a plurality of linear amplifiers, detectors and noise correlators connected to corresponding narrowband filters; and output switches connected to the linear amplifier to send the filtered signals into an adder. Both the undesired and desired signals are sent through the filtering system.
None of the above-identified references discloses a communication system having Off-line and In-line interference reduction devices for separating desired signals and undesired signals into different paths. Furthermore, none of the above-identified references disclose an Off-line signal interference reduction device connected to a TEE-junction of the communication system for shunting the undesired signals. Moreover, none of the above-identified references discloses an In-line signal interference reduction device coupled between the TEE-junction and the antenna system of the communication system for selectively filtering the desired signals.
All the references cited in the specification, and their references, are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background.